Any extension that restores FTP functionality?

Too bad that it is not possible to browse contents of FTP servers with Firefox anymore. So, once this functionality is gone from the main application, is there any extension that can provide the same functionality? I think there should be. When some big and important part of functionality is taken out of Firefox (like previously was removing RSS bookmarks), it should be simply moved to an extension, and not dropped completely…

Since Firefox no longer provides an FTP protocol implementation and extensions can’t directly access TCP sockets, I would assume that even if there is an extension, it will require a native counterpart. At which point it might just be more convenient to use software designed for FTP.

Of course I use FTP clients. But often something integrated with browser is better, especially when you encounter a “ftp://” link on a website (and there still are a lot of them).
Until now I didn’t find a FTP client that can be a drop-in replacement for what Firefox provided previously. If you know of any, please let me know.